TWI522980B - Driving method of display device and display device - Google Patents

Description

Display device driving method and display device

The present invention relates to a driving method for a display device including a gray scale storage display element. The invention is further related to display devices.

A display device including a gray scale storage display element such as an electrophoretic element has been favored as one of display devices that can be driven with low power consumption. The advantage of this device is that it is possible to maintain an image without a power source, and therefore, the display device is expected to be applicable to an e-book reader, a poster, or the like.

Display devices including a plurality of gray scale storage display elements have been proposed. For example, an active matrix display device formed by using a transistor as a switching element of a pixel in a liquid crystal display device or the like has been proposed (for example, refer to Patent Document 1).

Further, various methods of driving a display device have been proposed. For example, the following image switching method has been proposed: before displaying the image to be obtained, converting the entire display portion into a first gray level (for example, white), and when switching the image, it is then converted into a second gray level (for example, black) ( For example, refer to Patent Document 2).

[Reference case]

[Patent Document 1] Japanese Patent Application No. 2002-169190

[Patent Document 2] Japanese Patent Application No. 2007-206471

It is an object of an embodiment of the present invention to provide a driving method of a display device capable of performing multiple gray scale display.

Alternatively, it is an object of an embodiment of the present invention to provide a driving method of a display device for compressing residual images.

Alternatively, it is an object of an embodiment of the present invention to provide a driving method of a display device that achieves low power consumption.

Alternatively, it is an object of an embodiment of the present invention to provide a driving method of a display device capable of suppressing deterioration of components included in a display device.

Alternatively, it is an object of an embodiment of the present invention to provide a display device that operates by the above driving method.

An embodiment of the present invention is a driving method of a display device, the display device comprising a plurality of pixels each of which includes a gray scale storage display element, wherein a signal is input to one of the terminals, and a common potential is supplied to the other terminal . During the first initialization period, the first gray scale display level is displayed on the plurality of gray scale storage display elements included in the pixel portion by scanning the signal for the pixel portion a plurality of times. During the second initializing period after the first initializing period, the second gray scale display level is displayed by the pixel portion scanning signal at least once, and the plurality of gray scale storage display elements included in the pixel portion are displayed. In the address period after the second initializing period, the image is scanned in the pixel portion by a plurality of times to form an image on the pixel portion. During the first initialization period, the plurality of signals input to one of the terminals of the gray scale storage display element have different sustain periods.

Further, in addition to the above driving method, the driving method of the display device that performs signal scanning once on the pixel portion in the second initializing period is also an embodiment of the present invention.

Moreover, in addition to the above driving method, the driving method of the following display device is also an embodiment of the present invention: each of a plurality of signals input to one of the terminals of the grayscale storage display element during the first initializing period is shared. a potential, or a first potential different from the common potential; wherein each of the at least one signal input to one of the terminals of the gray scale storage display element during the second initializing period is a second potential, which produces a second And an electric field between the second potential and the common potential, which is opposite to an electric field generated by the difference between the first potential and the common potential; and is input to one of the terminals of the gray scale storage display element during the writing period Each of the signals is a common potential, a first potential or a second potential.

Moreover, in addition to the above driving method, the driving method of the following display device is also an embodiment of the present invention: each of a plurality of signals input to one of the terminals of the grayscale storage display element during the first initializing period is shared The potential is different from the first potential of the common potential; each of the at least one signal input to one of the terminals of the gray scale storage display element during the second initializing period is a common potential or a second potential, the second potential generating an electric field Between the second potential and the common potential, the direction is opposite to the electric field generated between the first potential and the common potential; and the plurality of signals input to one of the terminals of the gray scale storage display element during the writing period Each of them is a common potential, a first potential or a second potential.

Further, in addition to the above driving method, the driving method of the display device which inputs the common potential to one of the terminals of the gray scale storage display element in the last scan in the writing period is also an embodiment of the present invention.

Moreover, in addition to the above driving method, during the first initialization period, the plurality of signals are scanned x times (x is a natural number of 2 or more), and when the length of the shortest signal holding period is t, each of the plurality of signals is held. A driving method of a display device having a length of 2 ^yl t (y is a natural number of x or less) is also an embodiment of the present invention.

Further, in addition to the above driving method, the driving method of the display device having the same length of the plurality of signals input to one of the terminals of the gray scale storage display element during the writing period is also an embodiment of the present invention.

Moreover, a display device is also an embodiment of the present invention, comprising: a control unit for controlling the above driving method; a source driving portion and a gate driving portion electrically connected to the control portion; a transistor, a gate terminal thereof a sub-electrode is connected to the gate driving portion, a first terminal thereof is electrically connected to the source driving portion, and a second terminal electrode thereof is electrically connected to one of terminals of the electrophoresis element; and a capacitor has a terminal, and one terminal is electrically connected To the second terminal of the transistor, the other terminals are electrically connected to the wiring supplying the common potential.

Further, a display device using an oxygen semiconductor in a semiconductor layer of a transistor is also an embodiment of the present invention.

It should be noted that in the present specification, the gray scale storage display element can display the gray scale by the voltage application control and maintain the gray scale component under no voltage application. The following elements are provided as examples of gray scale storage display elements: an element using electrophoresis (electrophoresis element), a particle rotating element using a twisting ball, a charged coloring agent, or a particle moving element of Electronic Liquid Powder (registered trademark) A magnetic swimming element, a moving liquid element, a light scattering element, a phase change element, or the like, which displays gray scale by magnetic.

It should be noted that since the source terminal and the 汲 terminal of the transistor vary depending on the structure, operating conditions, and the like of the transistor, it is difficult to define which one is the source terminal or the 汲 terminal. Therefore, in this document (the specification, the patent application, the drawings, etc.), in order to distinguish, one of the source terminal and the terminal terminal is referred to as a first terminal, and the other is referred to as a second terminal.

In the driving method of the display device according to an embodiment of the present invention, the control of the voltage application time or the like can control the multiple gray scale display of the gray scale storage display element.

Moreover, the driving method of the display device according to an embodiment of the present invention includes an initialization process, wherein when the image is switched, the gray level of the plurality of grayscale storage display elements included in the pixel portion is converted into the first gray level, and then , converted to the second gray level. Therefore, an image with less residual previous images can be displayed.

Further, in the driving method of the display device according to the embodiment of the present invention, the lengths of the plurality of signal holding periods in which one of the terminals of the gray scale storage display element is input during the first initialization processing are different. Therefore, the number of signal scans required to apply a voltage to a plurality of electrophoretic elements displaying different gray scale levels in an appropriate time can be reduced. That is, deterioration of components included in the display device can be suppressed, and power consumption of the display device can be reduced.

Many embodiments of the invention are described in detail below with reference to the drawings. It is to be understood that the invention is not limited to the following description, and it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the present invention should not be limited to the description of the following examples.

(Example 1)

Referring to FIGS. 1A to 1C, 2, 3, 4, and 5, an example of the construction and operation of a display device including a gray scale storage display element and its operation will be described in the present embodiment. . It should be noted that an example in which an electrophoretic element is used as a gray scale storage display element is described in the present embodiment.

[Configuration Example of Display Device]

Fig. 1A is a block diagram showing the configuration of the display device of the embodiment. The display device 100 includes a pixel portion 101, a source driver 102, a gate driver 103, a control portion 104, m (m-type positive integer) source lines 105 ₁ to 105 _m which are arranged in parallel with each other, and n which are arranged in parallel with each other. (n is a positive integer) strip gate lines 106 ₁ to 106 _n . It is to be noted that the source driver 102 is electrically connected to the pixel portion 101 via m source lines 105 ₁ to 105 _m . The gate driver 103 is electrically connected to the pixel portion 101 via n gate lines 106 ₁ to 106 _n . Further, the control unit 104 is electrically connected to the source driver 102 and the gate driver 103.

Further, the pixel portion 101 includes n × m pixels 107 ₁₁ to 107 _nm . It should be noted that n × m pixels 107 ₁₁ to 107 _{nm are} arranged in n columns and m rows. Further, each of the m source lines 105 ₁ to 105 _m is electrically connected to n pixels, and the pixels are arranged in any one of the rows. Each of the n gate lines 106 ₁ to 106 _n is electrically connected to m pixels, and the pixels are arranged in any of the rows. In other words, the pixels 107 _ij disposed in the i-th column and the j-th row (i and j are positive integers) (1≦i≦n and 1≦j≦m) are electrically connected to the source line 105 _j and the gate line 106 _i .

Fig. 1B shows a circuit diagram of the pixels 107 _ij arranged in the i-th column and the j-th row. The pixel 107 _ij includes: a transistor 111 having a gate terminal electrically connected to the ith column gate line 106 _i and a first terminal electrically connected to the jth row source line 105 _j ; and a capacitor 112 having terminals One is electrically connected to the second terminal of the transistor 111, and the other terminals are electrically connected to the wiring (also referred to as a common potential line) for supplying the common potential (V _com ); the electrophoretic element 113 has terminals, one of which is electrically connected The second terminal of the transistor 111, and one of the terminals of the capacitor 112 and other terminals are electrically connected to the common potential line. It should be noted that in the present embodiment, the ground potential OV or the like can be given as the common potential (V _com ).

Fig. 1C shows a specific configuration example of the electrophoretic element 113. The electrophoretic element 113 shown in Fig. 1C includes an electrode 121, an electrode 122, and a layer 123 including charged particles and disposed between the electrode 121 and the electrode 122. Here, it is to be noted that the electrode 121 corresponds to one of the terminals of the electrophoretic element 113 in Fig. 1B, and the electrode 122 corresponds to the other terminal of the electrophoretic element 113 in Fig. 1B. Further, at least one of the electrode 121 and the electrode 122 is formed using a light transmitting material. Here, only the electrode 122 is formed using a light transmitting material. Further, the layer 123 containing the charged particles has a plurality of microcapsules 126, and a plurality of negatively charged white particles 124 and a plurality of positively charged black particles 125 are sealed in each of the microcapsules 126. It should be noted that the microcapsules 126 are filled with liquid, and the negatively charged white particles 124 and the positively charged black particles 125 can be moved in the microcapsules 126 by the electric field generated in the layer 123 containing the charged particles. Further, in the electrophoretic element 113, an insulating layer may be provided between the layer 123 containing the charged particles and the electrode 121 or the electrode 122.

In the display device 100 of the embodiment, it can be applied to electricity by control. The voltage of the swimming element 113 (including the electric field of the layer 123 of charged particles) concentrates the white particles 124 to one of the electrodes and concentrates the black particles 125 to the other electrodes. That is, the color of the electrophoretic element 113 (herein also referred to as the display of the electrophoretic element 113) observed from the electrode 122 of the optical transmission material can be controlled to be a color between white and black. Therefore, the image can be displayed in a pixel portion including a plurality of pixels, each of which has an electrophoretic element 113. Specifically, in the display device 100 of the present embodiment, a potential higher than the other terminals (electrodes 122) of the electrophoretic element 113 is applied to one of the terminals (electrode 121) of the electrophoretic element 113, so that the display of the electrophoretic element 113 is performed. It is black. A potential lower than the other terminals of the electrophoretic element 113 is applied to one of the terminals of the electrophoretic element 113, so that the display of the electrophoretic element 113 is white.

Moreover, the display of the electrophoretic element 113 in the display device 100 of the present embodiment is not limited to white and black (no need for binarization), and multiple gray scale displays can be displayed. For example, at least one intermediate color (gray) between white and black can be displayed. That is, multiple gray scale display can be performed by controlling the amount of white particles 124 and black particles 125 moving in the electrophoretic element 113 as a function of applied voltage and time value. It should be noted that the importance of the control function is that multiple gray scale displays can be performed in the display device to suppress temporal changes in the display image of the display device.

[Example of operation of display device]

The operation of the display device 100 of the present embodiment in displaying an image will be described below. Here, for convenience, the purest white of the display device is defined as gray level 1 (white), the darkest black of the display device is defined as gray level 8 (black), and the intermediate color between white and black is defined. The gray level is 2 to 7.

The other terminals of the electrophoretic element 113 included in the display device 100 of the present embodiment are electrically connected to a common potential line. Therefore, the display of the electrophoretic element 113 can be controlled by the potential supplied to one of the terminals of the electrophoretic element 113. Further, the potential of one of the terminals of the electrophoretic element 113 is controlled by the electric wire input from the source driver 102 via the transistor 111. Here, it should be noted that the source driver 102 can set the potential of the source line 105 _{j to} be higher than the potential of the common potential (V _com ) (V _H ), the same potential of the common potential (V _com ), or lower than the common potential ( Potential of V _com ) (V _L ).

That is, the source driver 102 supplies the potential (V _H ) to one of the terminals (electrode 121) of the electrophoretic element 113, and generates an electric field in the direction from the electrode 121 to the electrode 122 in the layer 123 containing the charged particles. Therefore, the gray level level displayed by the electrophoretic element 113 can be gray level level 8 (black) or gray level level close to gray level level 8 (black). Similarly, the potential (V _L ) is supplied to one of the terminals (electrode 121) of the electrophoretic element 113, and the electric field generated in the direction from the electrode 122 to the electrode 121 in the layer 123 containing the charged particles. Therefore, the gray level level displayed by the electrophoretic element 113 can be gray level level 1 (white) or gray level level close to the gray level level 1 (white). It should be noted that the gray level level displayed by the electrophoretic element 113 can be controlled by the electric field strength and the length of time generated by the electric field.

Here, for convenience, the following is explained: in the case where the timing of the signal scanning performed on the pixel portion 101 is defined as t, when the potential (V _H ) in the period t is supplied to one of the terminals of the electrophoretic element 113, the gray level is increased. 1, and when the potential (V _L ) in the period t is supplied to one of the terminals of the electrophoretic element 113, the gray scale level is decreased by one.

Further, the same potential of the common potential (V _com ) is supplied to one of the terminals (electrode 121) of the electrophoretic element 113, and no electric field is generated in the layer containing the charged particles. Therefore, the gray scale level displayed by the electrophoretic element 113 before the supply of the same potential can be maintained.

Next, each period of the display device 100 of the present embodiment will be described with reference to FIGS. 2 and 3.

Next, each period of the display device 100 of the present embodiment will be described with reference to FIGS. 2 and 3.

The use of the display device 100 of the present embodiment includes a switching period for rewriting an image and a display period for displaying an image. It is to be noted that, in the display device 100, the pixel portion 101 is scanned for a plurality of times during the switching period, but the pixel portion 101 is not scanned for signals during the display period.

It should be noted that, in the display device 100 of the present embodiment, for example, the signal scanning corresponds to the electric power contained in each of the gate line 106 _{1 selected} from the first column and the pixels 107 ₁₁ to 107 _{1 m} disposed in the first column. The crystal 111 is turned on, and the chirp signal is input from the source driver 102 to one of the terminals (electrodes 121) of the electrophoretic element 113 contained in the first column and the first row 107 ₁₁ to the gate line 106 _n in the nth column. And the transistor 111 included in each of the pixels 107 _n1 to 107 _nm disposed in the nth column is turned on, and the chirp signal is input from the source driver 102 to the electrophoretic element 113 contained in 107 _nm of the nth column and the mth row. Operation at one of the terminals (electrodes 121). This operation can be referred to as a signal scan.

Further, the switching period is divided into an initializing period for the initialization processing of the pixel portion 101 and a writing period for inputting the image data to the pixel portion 101. Further, the initializing period is divided into a first initializing period in which the electrophoretic element 113 displays the gray scale level 8 (black) and a second initializing period in which the electrophoretic element 113 is displayed to display the gray scale level 1 (white).

In the present specification, a process of displaying gray scale level 8 (black) (first initialization processing) and then displaying gray scale level 1 (white) (second initialization processing) is referred to as initialization processing. It should be noted that the initialization process enables the display device 100 to reduce residual images. Therefore, the initialization process is important for improving the display quality of the display device 100.

[First initialization processing]

In the display device 100 of the present embodiment, one of the terminals of the electrophoretic element 113 can be controlled during the first initialization process to supply a potential (V _H ) _thereto . Therefore, the display of the electrophoretic element 113 showing various gray scale levels is converted into gray scale level 8 (black).

It is to be noted that a problem occurs when the potential (V _H ) is also supplied to one of the terminals of the electrophoretic element 113 included in the pixel portion 101. In other words, in the same period, when a specific electric field is generated in all of the plurality of electrophoretic elements 113 provided in the pixel portion 101, a problem occurs.

I will explain the reasons below. The image has been displayed on the pixel portion 101. That is, the electrophoretic element 113 displaying the gray level 1 (white), the electrophoretic element 113 displaying the gray level 8 (black), and the electrophoretic element displaying the gray level 2 to 7 are arbitrarily present in the pixel portion 101. 113. The first initialization process is also performed on the electrophoretic element 113 in which the gray scale level 1 (white) is displayed and the electrophoretic element 113 which displays the gray level level 8 (black). In other words, supplying the excess potential (V _H ) to the electrophoretic element 113 displaying the gray level 8 (black) is an electrical waste. Here, the electrophoretic element 113 showing the gray level 1 (white) and the electrophoretic element 113 displaying the gray level 8 (black) are compared. However, a problem also occurs when the first initialization process is performed uniformly on the electrophoretic element 113 displaying different gray scale levels. Therefore, it is preferable to consider the gray scale level displayed by the electrophoretic element 113 during the previous display period, and perform the first initialization processing individually on each of the plurality of electrophoretic elements 113. Specifically, it is preferable to control the display device such that the potential (V _H ) is applied to one of the terminals of the electrophoretic element 113 that briefly displays the gray level level close to the gray level level 8 (black), and the potential ( V _H ) is applied to one of the terminals of the electrophoretic element 113 which briefly displays the gray level level 1 (white) or the gray level level close to the gray level level 1 (white).

Figure 2 shows the signal scanning of the electrophoresis element 113 during the initialization process. In the display device 100 of the present embodiment, the potential of each of the electrophoretic elements 113 is controlled by the time gray scale method during the first initialization processing period. It should be noted that the time gray scale method is controlled by controlling the time during which the voltage is applied to each of the electrophoretic elements 113: each of the periods applied to the electrophoretic element 113 during each period formed by the further division of the first initialization processing period The method of voltage of one.

Further, in the present embodiment, in addition to the division in the first initializing period, as shown in Fig. 2, the weighting of each period (time change of the period) is performed. Fig. 2 shows that the first initialization period is divided into a first period (T1), a second period (T2), and a third period (T3), and weighting is performed to satisfy, for example, T1:T2:T3=1:2:4. It should be noted that in the present embodiment, t represents the time required for one signal scanning of the display device 100 of the present embodiment. As shown in Fig. 2, the application time of the appropriate voltage can be weighted by the holding period of each signal (the period from when the signal is input to one of the terminals of the electrophoretic element 113 to the time when the next signal is input) in eight ways. (Including the case where the voltage application time is 0), it is controlled after three signal scans.

As illustrated, a voltage can be applied to each of the electrophoretic elements 113, which is weighted to control the voltage applied to the electrophoretic element 113 during the first initialization period, thereby performing multiple gray scale display for an appropriate time. In addition, reducing the number of signal scans reduces power consumption. The better one is as shown in Fig. 2, and the weighting of the signal holding period is performed. That is, preferably, when the signal scanning is performed x (x is a natural number of 2 or more), weighting is performed to change the holding period as t, 2t, 4t, ... 2 ^{x - 1} t. This is because, by weighting in this way, the voltage application time of the minimum unit t can be controlled by the minimum number of signal scans.

[Second initialization processing]

Examples of the display control apparatus 100 according to the present embodiment, to serve during the second initialization process, the electric potential (V _L) supplied to the electrophoretic element 113 of one of the terminals. Therefore, the gray scale level displayed by the gray scale level 8 (black) display is converted into gray scale level 1 (white).

It is to be noted that the same potential can be supplied to the plurality of electrophoretic elements 113 in the pixel portion 101 during the second initialization processing. That is, since the gray scale level of all of the plurality of electrophoretic elements 113 included in the pixel portion 101 is converted to the gray scale level 8 (black) during the first initialization processing period.

Figure 2 shows the signal scan of the electrophoretic element 113 during the initialization period. In the display device 100 of the present embodiment, the signal scanning such as the second initialization processing is performed only once at the beginning of the period. The potential (V _L ) is supplied to one of the terminals of the electrophoretic element 113 in the pixel portion 101, and the gray level level duration displayed by each of the electrophoretic elements 113 is converted from the gray level level 8 (black) to the gray level position. Standard 1 (white). It should be noted that since the gray level level 8 (black) is converted to the gray level level 1 (white), the length of the second initialization processing period must be at least 7 t or longer.

Further, when the length of the second initialization processing period is 8t as shown in FIG. 2 and the period is as shown in the fourth period (T4), the weighting of the entire initialization processing period can be performed to satisfy T1: T2: T3: T4 = 1:2:4:8.

As described above, the residual image occurring in the display image can be reduced by the initialization process. Further, in the above initialization processing, the number of signal scans can be reduced by the weighting of the signal holding period.

It should be noted that in the display device 100, the capacitance of the capacitor 112 provided for the pixel 107 must be large, and the display period can be longer. Therefore, the current supply capability of the transistor 111 provided for the pixel 107 must be large. In particular, the size of the transistor must be large. As a result, the load of the source driver 102 that supplies the electric charge to the capacitor 112 and the load of the gate driver 103 that controls the switch of the transistor 111 increase. Therefore, an element such as a transistor which forms the source driver and the gate driver 103 is deteriorated, so that the problem is heavy. In contrast, deterioration of components such as transistors can be suppressed by reducing the number of signal scans during the initialization period as described above.

[formation of images]

In the display device 100 of the present embodiment, a potential (V _H ), a potential (V _L ), and a potential (V _com ) are selectively supplied to one of the terminals of the electrophoretic element 113 during the writing period to control the electrophoretic element. 113 shows the gray scale. Here, for convenience, the potential (V _H ) is supplied to one of the terminals of the electrophoretic element 113 to t (the time required for signal scanning), and the display gray scale of the electrophoretic element 113 is converted to 1 level (for example, gray scale level 1) (white) converted to grayscale 2). Therefore, by having a gray scale method of 7 t in the writing period, the display gray scale level of the electrophoretic element 113 can be appropriately set to gray scale level 1 (white) to gray scale level 8 (black). Further, the display gray scale of the electrophoretic element 113 included in each of the pixels 107 is controlled, and the 俾 image can be formed on the pixel portion 101.

It should be noted that it is preferable not to weight the signal holding period during the writing period, although the weighting may be performed as in the initializing period. This is because the gray scale level of the display of the electrophoretic element 113 can be accurately displayed by considering not only the time when the voltage is applied to the electrophoresis element 113 but also the voltage application sequence during the writing period.

Moreover, the signal scanning is not performed on the pixel portion 101 in the display period after the writing period. That is, the signal input to the pixel portion 101 at the end of the writing period determines the state during the display period. Therefore, it is preferable that the common potential (V _com ) is supplied to one of the terminals of the electrophoretic element 113 in the pixel portion 101 at the end of the writing period, and the control is not applied to the electrophoretic element 113 during the display period. This is because it is preferable to display that the gray scale level is converted into a state in which a voltage is applied to the electrophoretic element 113, or the electrophoretic element 113 may be deteriorated by applying a constant voltage for a long time.

In view of the above description, FIG. 3 shows that the writing period is divided into the fifth period (T5) to the twelfth period (T12), and this period is shown as t. It should be noted that it also explains that the write period includes the use of the common potential (V _com ) input period during t during the gray scale control period of 7t period.

[Specific example]

Referring to Figures 4 and 5, the operation of the display device during the switching period will be described. Specifically, the following case is explained: an image (a first image) of a circle displayed by the gray level level 5 and a circle displayed by a gray level level 8 (black), on which the gray level is 1 ( White) The display background is changed to an image of the circle (second image) moved from the left to the center, and the second image is further changed to an image of the circle (third image) moved from the center to the right side.

It should be noted that the switching period of the first image changed to the second image is 1, and the switching period of the second image to the third image is 2. Moreover, the pixel on the center of the circle displayed by the gray level level 5 in the first image is the pixel A, and the pixel on the center of the circle displayed by the gray level level 5 in the third image is the pixel B.

Further, from the source driver, a common potential (V _com ), a potential higher than the common potential (V _com ), and a potential lower than the common potential (V _com ) (V _L ) can be input to the terminals of the electrophoretic element 113 included in each pixel. one.

First, referring to Fig. 4, the signal scanning during the switching period and the signals input to the pixels A and B will be described.

When the switching signal for switching from the first image to the second image is input from the control unit to the source driver and the gate driver, the first initialization period is performed in accordance with the gray level level displayed on each pixel. Here, three signal scans are performed during the first initialization period. The interval between the first scan of the signal and the second scan of the signal (the duration of the hold of the first signal) is t. The interval between the second scan of the signal and the third scan of the signal (the period during which the second signal is held) is 2t. The interval between the third scan of the signal and the end of the first initialization period (the period during which the third signal is held) is 4t. That is, the first initialization period is weighted by the hold period of the signal. Therefore, three signal scans are performed on the pixels, and the pixels are arbitrarily set for the pixel portion and displayed in eight gray scale levels, and the gray scale levels of all the pixels in the pixel portion can be applied by voltage for an appropriate time. Convert to gray level level 8 (black). Specifically, all of the signals supplied to the first to third signals of the pixel A displaying the gray level 8 (black) share the potential (V _com ) and are supplied to the pixel displaying the gray level 1 (white). All signals of the first to third signals of B share the potential (V _H ), and the display of the pixels A and B can be gray level 8 (black).

Next, a second initialization process is performed. Here, a signal scan is performed in the second initialization process. The potential (V _L ) is also input to each pixel. Also, the length of time of the second initialization process is set to 7t or longer to change the display of all pixels to grayscale level 1 (white).

Second, a second image is formed. Here, eight signal scans are performed during the writing period. Input the input signal individually to all pixels. It should be noted that the weighting of the holding period of each signal is not performed, and the interval of signal scanning is also t. The pixels A and B in the second image are displayed in gray level 5 . Therefore, during the writing period, the input signal can be appropriately controlled so that (the period of the input potential (V _H )) - (the period of the input potential (V _L )) = 4t. Preferably, the specific type of signal input for displaying the gray level level to be obtained is appropriately set because the signal is determined based on the number of charged particles or the applied voltage in the electrophoretic element during the writing period. For example, it is preferable to input the potential (V _L ) after inputting the excess potential (V _H ) as the input signal to the pixel B, because it can suppress the localization of the charge of the layer containing the charged particles in the electrophoretic element. . Further, it is preferable that a common potential (V _com ) is input to all the pixels in the scanning of the last signal in the writing period, and no voltage is applied to the electrophoretic element during the display period of the second image.

In this way, switching from the first image to the second image is completed. Here, a signal is input to the pixel A and the pixel B during the display period of the second image. Further, the potential of one of the terminals of the electrophoretic element included in the pixel A and the pixel B is maintained at the same potential as the common potential (V _com ), and a voltage is applied to the electrophoretic element (the electric field is not generated in the layer containing the charged particles). Therefore, the display of the second image can be maintained. It is to be noted that the second image can be held until the switching signal for switching to the subsequent third image is input from the control unit to the source driver and the gate driver.

Next, the scanning of the signal and the signals input to the pixels A and B in the switching period 2 will be described with reference to FIG.

When the switching signal for switching from the second image to the third image is input from the control unit to the source driver and the gate driver, the first initialization period is performed in accordance with the gray scale level displayed on each pixel. Here, three signal scans are performed during the first initialization period. The interval between the first scan of the signal and the second scan of the signal (the duration of the hold of the first signal) is t. The interval between the second scan of the signal and the third scan of the signal (the period during which the second signal is held) is 2t. The interval between the third scan of the signal and the end of the first initialization period (the period during which the third signal is held) is 4t. That is, the first initialization period is weighted by the hold period of the signal. Therefore, three signal scans are performed on the pixels, and the pixels are arbitrarily set for the pixel portion and displayed in eight gray scale levels, and the gray scale levels of all the pixels in the pixel portion can be applied by voltage for an appropriate time. Convert to gray level level 8 (black). Specifically, the potentials (V _H ) as the first and third signals and the pixel A and the pixel B supplied to the gray scale level 5 as the third signal are used as the common potential (V _com ) of the third signal. To display the pixel A and the pixel B of the gray level level 5, the display of the pixel A and the pixel B can be gray level 8 (black).

Next, a second initialization process is performed. Here, a signal scan is performed in the second initialization process. The potential (V _L ) is also input to each pixel. Also, the length of time of the second initialization process is set to 7t or longer to change the display of all pixels to grayscale level 1 (white).

Second, a third image is formed. Here, 8 signal scans are performed during the writing period. The input signal is individually input to all pixels. It should be noted that the weighting of the holding period of each signal is not performed, and the time interval of the signal scanning is also t. The pixel A in the third image is displayed in gray level 1 (white). Therefore, during the writing period, the input signal can be appropriately controlled so that (the period of the input potential (V _H )) - (the period of the input potential (V _L )) = 0. It should be noted that, for example, the case where all eight signal systems input to the pixel A share the potential (V _com ) will be described. The pixel B in the third image is displayed in gray level 8 (black). Therefore, during the writing period, the input signal can be appropriately controlled so that (the period of the input potential (V _H )) - (the period of the input potential (V _L )) = 7t. It should be noted that since the writing period is 8t here, the gray level level 8 (black) cannot be freely displayed. However, since it is appropriately selected to display the gray scale level 8 (black), it is preferable that the writing period is longer. Further, it is preferable that the common potential (V _com ) is input to all the pixels during the last signal scanning in the writing period, and the voltage is not input to the electrophoresis element during the display period of the third image.

In this way, switching from the second image to the third image is completed.

[Modification]

The above display device is an example of an embodiment. This embodiment includes a display device having the features not described above.

Although the above description shows, for example, a display device having an electrophoretic element of 8 gray scale levels (gray level 1 (white) to gray level 8 (black)) can be used, but can also display higher gray scale or Lower grayscale display device. Further, the use of negatively charged white particles and positively charged black particles as an example of charged particles contained in the electrophoretic element is acceptable, and the white particles are positively charged and the black particles are negatively charged, or the two colors are Particles other than (white and black). Moreover, a charged particle and a dyed particle may be sealed in the microcapsule, and the gray scale is displayed by the movement of the charged particle.

Further, in the above device, the relationship between the voltage application time and the gray level level displayed by the electrophoretic element is simplified for convenience, but the relationship may be complicated by the display device. In other words, it is assumed that the voltage application time is linear with the gray level level displayed by the electrophoretic element, but the relationship may be a nonlinear relationship. In this case, the weighting of the signal holding period can be appropriately determined, and the holding period is not determined to be a multiple of 2.

Further, in the above display device, it is assumed that the gray scale level of the electrophoretic element is maintained without being converted during the display period. However, when the image retention period becomes long, the display image may deteriorate over time. For example, even when a voltage is not applied between the pair of electrodes of the electrophoretic element showing the gray level 8 (black), the positively charged black particles and the negatively charged white particles are not set at the display gray level. 8 (black) in the microcapsules contained in the electrophoresis element. Therefore, during the image writing period, the electric field is not generated in the microcapsule, and the gray scale level is displayed to be converted from the gray level of the input. In this case, during the first initialization period, the potential (V _H ) can be input to the electrophoresis element for the display of the gray scale level 8 (black), and the signal is input to the electrophoresis during the previous writing period. element.

Further, in the above display device, weighting is performed such that the signal holding period continues to be longer during the first initializing period. However, weighting may be performed such that during the first initialization period, the signal holding period is continued to be shorter, or weighting is performed, so that the signal holding period is arbitrarily changed.

Further, in the above display device, only one signal scanning is performed in the second initializing period. However, when the second initialization period becomes longer or the pixel portion of the display device has a high resolution, the gray scale level of the electrophoretic element may not be converted to gray scale level 1 (white). For example, the first signal input at the beginning of the second initialization period may leak through the transistor before the display of the gray level of the electrophoretic element is completed. Moreover, when the size of the capacitor is small due to high resolution, such leakage becomes severe. In which case, during the second initialization potential (V _L) may be input to the electrophoretic element multiple times. It should be noted that in the case of performing a plurality of signal scans in the second initializing period, the weighting of the holding period may be performed as in the first initializing period, or the length of each holding period of the signal may be the same. Further, at least one of the signals input to the plurality of signals may be subjected to a common potential (V _com ).

Further, in the present embodiment, an electrophoretic element is used as an example of a gray scale storage display element. However, the driving method explained in the embodiment is not limited to the display device including the electrophoretic element. In other words, the driving method described in this embodiment can be applied to a display device including an element (gray scale storage display element) that can control the display of gray scale levels and can maintain the display gray scale position without voltage application. quasi. For example, the driving method of the present embodiment can be used to display a display device that performs display by using a voltage and a black and white twisting ball, and display by using Electronic Liquid Powder (registered trademark) or the like. Display device.

It is to be understood that all or a part of the contents described in the embodiments may be combined with all or a part of the contents described in any of the other embodiments.

(Example 2)

An example of the display device in the first embodiment will be described in the present embodiment. Specifically, the configuration of the pixels in the pixel portion will be described with reference to FIGS. 6A and 6B. It should be noted that in the present embodiment, for example, an electrophoretic element is used as a gray scale storage display element.

(Example 2)

Fig. 6A is a plan view of the pixel of the present embodiment, and Fig. 6B is a cross-sectional view taken along line A-B of Fig. 6A. The display device in FIGS. 6A and 6B includes a substrate 600, a thin film transistor 601 and a capacitor 602 disposed above the substrate 600, an electrophoretic element 603 disposed above the thin film transistor 601 and the capacitor 602, and disposed above the electrophoretic element 603. Substrate 604. It is to be noted that the electrophoretic element 603 is omitted in Fig. 6A.

The thin film transistor 601 includes a conductive layer 610 electrically connected to the gate line 630, an insulating layer 611 disposed over the conductive layer 610, a semiconductor layer 612 disposed over the insulating layer 611, over the semiconductor layer 612, and a source line 631. The conductive layer 610 is used as a gate terminal of the thin film transistor 601, a conductive layer 613, and a conductive layer 614. It should be noted that the conductive layer 610 is used as the gate terminal of the thin film transistor 601, the conductive layer 613 is used as the first terminal of the thin film transistor 601, and the conductive layer 614 is used as the second terminal of the thin film transistor 601. Further, it can be expressed as a portion of the conductive layer 610 that is a gate line 630, and the conductive layer 613 is a portion of the source line 631.

The capacitor 602 includes a conductive layer 614, an insulating layer 611, and a conductive layer 615 electrically connected to the common potential line 632. It should be noted that the conductive layer 614 is used as one of the terminals of the capacitor 602, the insulating layer 611 is used as a dielectric, and the conductive layer 615 is used as the other terminal of the capacitor 602. It can also be expressed that the conductive layer 615 is part of the common potential line 632.

The electrophoretic element 603 includes: a pixel electrode 616 electrically connected to the conductive layer 614 provided at the opening of the insulating layer 620; a counter electrode 617 to which the same potential as the conductive layer 615 is applied; and a layer 618 containing charged particles, and It is provided between the pixel electrode 616 and the counter electrode 617. It should be noted that the pixel electrode 616 is used as one of the terminals of the electrophoretic element 603, and the counter electrode 617 is used as the other terminal of the electrophoretic element 603.

As illustrated in Embodiment 1, the display device of the present embodiment can control the movement of the charged particles diffused on the layer 618 containing the charged particles by controlling the voltage applied to the layer 618 containing the charged particles. Further, in the display device of the present embodiment, the counter electrode 617 and the substrate 604 have optical transmission properties. That is, the display device of this embodiment is a reflective display device in which the display surface is on the side of the substrate 604.

Materials for the respective components of the display device of the present embodiment are provided below.

a semiconductor substrate (for example, a single crystal substrate and a germanium substrate), an SOI substrate, a glass substrate, a quartz substrate, a conductive substrate provided with an insulating layer on the surface, or a flexible substrate such as a plastic substrate, an adhesive film, a paper containing a fibrous material And a substrate film as the substrate 600. Examples of the glass substrate include a borosilicate glass substrate, an aluminoborosilicate glass substrate, and a soda lime glass substrate. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenyl hydrazine (PES) or acrylic acid can be used for the flexible substrate.

It can be selected from aluminum (Al), copper (Cu), titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), chromium (Cr), niobium (Nd) and antimony (Sc), including An alloy of any of these elements, or a nitride of any of these elements, serves as the conductive layer 610 and the conductive layer 615. Stacked constructions of these materials can also be used.

As the gate insulator 611, an insulator such as hafnium oxide, tantalum nitride, hafnium oxynitride, tantalum nitride oxide, aluminum oxide or tantalum oxide can be used. Stacked constructions of these materials can also be used. It should be noted that tantalum nitride refers to more oxygen than nitrogen, and is from 55 atomic percent to 65 atomic percent, from 1 atomic percent to 20 atomic percent, and from 25 atomic percent, respectively, at a total atomic percentage of 100 atomic percent. A substance containing oxygen, nitrogen, helium, and hydrogen in a predetermined concentration range of 35 atomic percent and from 0.1 atomic percent to 10 atomic percent. Further, the tantalum nitride film refers to nitrogen containing more than oxygen, and at a total atomic percentage of 100 atomic percent, respectively, from 15 atomic percent to 30 atomic percent, from 20 atomic percent to 35 atomic percent, from 25 A film containing oxygen, nitrogen, helium and hydrogen in a predetermined concentration range from atomic percentage to 35 atomic percent and from 15 atomic percent to 25 atomic percent.

It is possible to use a group 14 whose main component belongs to the periodic table, such as germanium (Si) and germanium (Ge), compounds such as germanium (SiGe) and gallium arsenide (GaAs), oxides such as zinc oxide (ZnO), and indium (In) And a material of zinc oxide of gallium (Ga), or a semiconductor material such as an organic compound having semiconductor characteristics, as the semiconductor layer 612. Further, a stacked layer formed of such a semiconductor material may also be used.

It can be selected from aluminum (Al), copper (Cu), titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), chromium (Cr), niobium (Nd) and antimony (Sc), including An alloy of any of these elements, or a nitride of any of these elements, serves as the conductive layer 613 and the source line 631. Stacked constructions of these materials can also be used.

As the gate insulating layer 620, a ruthenium oxide layer, a tantalum nitride layer, a hafnium oxynitride layer or a tantalum nitride oxide layer, an insulator such as aluminum oxide or tantalum oxide may be used. Alternatively, an organic material such as polyamide, polyvinylphenol, benzocyclobutene, acrylic or epoxy resin; a silicone material such as a silicone resin; oxazole or the like can also be applied. The siloxane contains a chemical structure formed by the bond of cerium (Si) and oxygen (O). An organic group such as a hydrocarbon group or an aromatic hydrocarbon or a fluorine group can be used. The organic group may contain a fluorine group.

It can be selected from aluminum (Al), copper (Cu), titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), chromium (Cr), niobium (Nd) and antimony (Sc), including An alloy of any of these elements, or a nitride of any of these elements, serves as the pixel electrode 616. Stacked constructions of these materials can also be used. Further, for example, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium tin oxide, indium zinc oxide, and indium tin oxide added with antimony oxide can be used. Wait.

Titanium oxide can be used to charge positively charged particles, and carbon black can be used to charge negatively charged particles as charged particles contained in layer 618 containing charged particles. It is to be noted that a single material selected from a conductive material, an insulating material, a semiconductor material, a magnetic material, a liquid crystal material, a ferroelectric material, an electrochromic material, or an electrophoretic material, or a composite material of any of these materials may be used.

Conductive materials having optical transmission properties such as indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium tin oxide, indium zinc oxide Or add indium tin oxide such as yttrium oxide.

The substrate 604 can be formed using a light-transmitting substrate represented by a glass substrate, such as a bismuth borate glass substrate, an aluminoborosilicate glass substrate, a soda-lime glass substrate, or using polyethylene terephthalate (PET) or the like.

It is to be understood that all or a part of the contents described in the embodiments may be combined with all or a part of the contents described in any of the other embodiments.

(Example 3)

An example of a thin film transistor different from the transistor contained in the display device of Embodiment 2 will be described with reference to Figs. 7A to 7D in this embodiment. 7A to 7D show an example of a thin film transistor which can be applied to the thin film transistor of Example 2.

In FIGS. 7A to 7D, the thin film transistor 700 is disposed above the substrate 701. Further, an insulating layer 702 and an insulating layer 707 are disposed over the thin film transistor 700.

The thin film transistor 700 in Fig. 7A has a structure in which the low-resistance semiconductor layers 706a and 706b are provided between the conductive layers 703a and 703b as the first and second terminals and the semiconductor layer 704. The conductive layers 703a and 703b are in ohmic contact with the semiconductor layer 704 by the low resistance semiconductor layers 706a and 706b. It should be noted that the low-resistance semiconductor layers 706a and 706b are semiconductor layers having a lower resistance than the semiconductor layer 704.

The thin film transistor 700 in Fig. 7B is a bottom gate thin film transistor having a structure in which a semiconductor layer 704 is provided over the conductive layers 703a and 703b.

The thin film transistor 700 in Fig. 7C is a bottom gate thin film transistor having a structure in which a semiconductor layer 704 is provided over the conductive layers 703a and 703b. Further, the low-resistance semiconductor layers 706a and 706b are provided between the conductive layers 703a and 703b as the first and second terminals and the semiconductor layer 704.

The thin film transistor 700 in Fig. 7D is a top gate thin film transistor. A semiconductor layer 704 including low-resistance semiconductor layers 706a and 706b as a source region and a drain region is provided over the substrate 701. An insulating layer 708 is disposed over the semiconductor layer 704. A conductive layer 705 for use as a gate terminal is disposed over the insulating layer 708. Further, conductive layers 703a and 703b which are in contact with the respective low-resistance semiconductor layers 706a and 706b as the first terminal and the second terminal are provided.

A thin film transistor having a single gate structure is described in this embodiment. However, the thin film transistor may have a double gate structure or the like. In this case, a gate electrode layer may be provided above and below the semiconductor layer, or a plurality of gate electrode layers may be provided only on one side (upper or lower side) of the semiconductor layer.

Further, the material for the semiconductor layer of the thin film transistor is not particularly limited. An example of a material that can be used for a semiconductor layer of a thin film transistor will be described.

The semiconductor layer included in the semiconductor element can be formed using a semiconductor material gas represented by silane or decane, an amorphous semiconductor fabricated by a sputtering method or a vapor phase growth method, and amorphous by using light energy or thermal energy. A polycrystalline semiconductor formed by semiconductor crystallization; a single crystal semiconductor (also referred to as semi-amorphous or microcrystalline). The semiconductor layer can be formed by a sputtering method, an LPCVD method, a CVD method, or the like.

Considering the Giss free energy, the microcrystalline semiconductor belongs to the metastable state between the amorphous and the single crystal. That is, the microcrystalline semiconductor film has a stable third state in terms of free energy, and has a short program and a lattice distortion effect. The columnar or needle crystal grows in a direction orthogonal to the surface of the substrate. A typical example of a microcrystalline semiconductor has a microcrystalline germany Rayman spectrum at a wave number below 520 cm ^-1 , which represents the peak of the Lehman spectrum of a single crystal germanium. That is, the peak of the microcrystalline Raman spectrum exists between 520 cm ^-1 representing a single crystal germanium and 480 cm ^-1 representing an amorphous germanium. Further, in order to terminate the levitation bond, the microcrystalline cerium contains at least 1 atomic percent or more of hydrogen or halogen. Moreover, the microcrystalline germanium contains, for example, helium, argon, neon or krypton to further promote the lattice distortion effect, increase the stability, and obtain a favorable microcrystalline semiconductor.

The microcrystalline semiconductor film can be formed by a high frequency plasma CVD method at a frequency of tens to hundreds of kHz or by a microwave plasma CVD apparatus at a frequency of 1 GHz or higher. The microcrystalline semiconductor film can be generally formed using a dilute solution of hydrogen hydride such as SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₃ , SiCl ₄ or SiF ₄ . The microcrystalline semiconductor film can be formed by a diluent of one or more rare gas elements of cerium, argon, krypton and neon, in addition to hydrogen hydride and hydrogen. In this case, the flow ratio of hydrogen to hydride is set to 5:1 to 200:1, preferably 50:1 to 150:1, and more preferably 100:1.

A typical example of an amorphous semiconductor is hydrogenated amorphous germanium, and a typical example of a crystalline semiconductor is polyfluorene or the like. Examples of polyfluorene (polycrystalline germanium) include: a so-called high-temperature polyfluorene which contains polyfluorene as a main component and is formed at a treatment temperature of 800 ° C or higher; so-called low-temperature polyfluorene, which contains as a main component The polyfluorene is formed at a treatment temperature of 600 ° C or higher; a polyfluorene obtained by crystallizing an amorphous crucible such as an element which promotes crystallization, or the like. Needless to say, a microcrystalline semiconductor or a semiconductor partially containing a crystal phase may also be used as described above.

Alternatively, not only simple substrates such as germanium (Si) or germanium (Ge), but also such as potassium arsenide GaAs, indium phosphide InP, tantalum carbide SiC, zinc selenide ZnSe, potassium nitride GaN or germanium telluride SiGe can be used. As a material of the semiconductor layer.

In the case of using a crystalline semiconductor in a semiconductor layer, a crystalline semiconductor film can be produced by various methods such as a laser crystallization method, a thermal crystallization method, or a thermal crystallization method using an element such as nickel which promotes crystallization. Further, when the microcrystalline semiconductor belonging to the SAS is crystallized by laser irradiation, crystallization can be enhanced. The amorphous germanium layer is heated at 500 ° C for 1 hour in a nitrogen atmosphere before introduction of the element which promotes crystallization, and the hydrogen is released until it is in the amorphous germanium film. The hydrogen concentration is changed to 1 × 10 ²⁰ atoms/cm ³ . This is because the hydrogen-rich amorphous germanium film can be destroyed by laser radiation.

The method of adding the metal element to the amorphous semiconductor film is not particularly limited as long as the metal element may exist on the surface or inside of the amorphous semiconductor film. For example, a sputtering method, a CVD method, a plasma processing method (for example, a plasma CVD method), an absorption method, or a method of coating a metal salt solution may be used. Among them, the method of using the solution is simple, and it is advantageous in that the concentration of the metal element can be easily controlled. Further, at this time, preferably, an oxide film is deposited to improve the surface of the amorphous semiconductor film by UV light irradiation in an oxygen atmosphere, thermal oxidation, treatment with ozone water containing hydrogen radicals or hydrogen peroxide, or the like. The water is wet and coated with an aqueous solution on the entire surface of the amorphous semiconductor film.

Further, in the crystallization step of crystallizing the amorphous semiconductor film to form the crystalline semiconductor film, an element (also referred to as a catalyst element) which promotes crystallization may be added to the amorphous semiconductor film, and may be heat-treated (at 500 ° C to 750 Crystallization was carried out at 3 ° or 24 hours at °C. Iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), copper (Cu) ) and gold (Au), etc. as elements that promote (accelerate) crystallization.

In order to remove or reduce an element which promotes crystallization from the crystalline semiconductor film, the semiconductor film containing the impurity element is brought into contact with the crystalline semiconductor film to serve as a deuterium region. As the impurity element, an impurity element imparting n-type conductivity, an impurity element imparting p-type conductivity, a rare gas element or the like can be used. For example, phosphorus (P), nitrogen (N), arsenic (As), antimony (Sb), antimony (Bi), boron (B), antimony (He), neon (Ne), argon (Ar),氪 (Kr) and 氙 (Xe) select one or more elements. A semiconductor film containing a rare gas element is formed to be in a crystalline semiconductor film with an element which promotes crystallization, followed by heat treatment (from 550 ° C to 750 ° C for 3 minutes to 24 hours). The element for promoting crystallization contained in the crystalline semiconductor film is transferred into the semiconductor film containing the rare gas element, thereby removing or reducing the element which promotes crystallization contained in the crystalline semiconductor film. Thereafter, the semiconductor film containing the rare gas element used as the deuterium region is removed.

The amorphous semiconductor can be crystallized by heat treatment and application of laser light radiation, or several times of heat treatment or laser light irradiation.

The crystalline semiconductor film can also be formed directly on the substrate by a plasma method. Alternatively, the crystalline semiconductor film may be selectively formed directly on the substrate by a plasma method.

Further, an oxide semiconductor can be used as the material of the semiconductor layer. For example, zinc oxide (ZnO), tin oxide (SnO ₂ ), or the like can be used. In the case of using zinc oxide (ZnO) in the semiconductor layer, a stacked layer of Y ₂ O ₃ , Al ₂ O ₃ , and TiO ₂ may be used, which is equal to the gate insulating layer, and ITO, Au, and Ti may be used to be equal to the gate electrode layer and source. a pole electrode layer and a drain electrode layer. Further, indium In, gallium Ga or the like may be applied to zinc oxide (ZnO).

A film expressed by InMO ₃ (ZnO) _m (m>0) can be used. Here, M represents one or more metal elements selected from the group consisting of gallium Ga, aluminum Al, manganese Mn, and cobalt Co. For example, M may be gallium Ga, gallium Ga, and aluminum Al, gallium Ga, and manganese Mn, gallium Ga, cobalt Co, and the like. An oxide semiconductor film containing gallium Ga as M is called indium In-Ga-Zn-O (indium-gallium-zinc-oxygen) between the compositional formulas represented by InMO ₃ (ZnO) _m (m is greater than 0). An oxide semiconductor, an In-Ga-Zn-O-based oxide semiconductor is also called an In-Ga-Zn-O-based non-single-crystal film.

An oxide semiconductor coated as an oxide semiconductor layer is an oxide of a tetrametal component such as an In-Sn-Ga-Zn-O (indium-tin-gallium-zinc-oxygen) film, such as the one provided above. In-Ga-Zn-O (indium-gallium-zinc-oxygen) film, In-Sn-Zn-O (indium-Sn-zinc-oxygen) film, In-Al-Zn-O (indium-aluminum-zinc- Oxygen) film, Sn-Ga-Zn-O (tin-gallium-zinc-oxygen) film and oxide of three metal components of Al-Ga-Zn-O (aluminum-gallium-zinc-oxygen) film, and Sn- Al-Zn-O (tin-aluminum-zinc-oxygen) film, or such as In-Ga-O (indium-gallium-oxygen) film, In-Zn-O (indium-zinc-oxygen) film, Sn-Zn -O (tin-zinc-oxygen) film, Al-Zn-O (aluminum-zinc-oxygen) film, Zn-Mg-O (zinc-magnesium-oxygen) film, Zn-Mg-O (zinc-magnesium-oxygen) Film, Sn-Mg-O (tin-magnesium-oxygen) film, In-Mg-O (indium-magnesium-oxygen) film, In-O (indium-oxygen) film, Sn-O (tin-oxygen) film And an oxide of the two metal components of the Zn-O (zinc-oxygen) film. Further, SiO ₂ may be contained in the oxide semiconductor film.

A thin film transistor using such an oxide semiconductor as a semiconductor layer has a high field effect mobility. Therefore, the thin film transistor can be used not only as a transistor in the pixel portion but also as a transistor for forming a gate driver or a source driver. That is, the pixel portion and the gate driver or the source driver may be formed over the same substrate. As a result, preferably, the manufacturing cost of the display device can be reduced.

It is to be understood that all or a part of the contents described in the embodiments may be combined with all or a part of the contents described in any of the other embodiments.

(Example 4)

In the present embodiment, an application example of the display device described in the above embodiment will be described with reference to specific examples shown in Figs. 8A to 8D.

FIG. 8A shows a portable information terminal including a housing 3001, a pixel portion 3002, an operation button 3003, and the like. The display device described in the above embodiments can be applied to a display device including the pixel portion 3002.

Fig. 8B shows an example of an e-book reader, which in the above embodiment includes a display device. The first housing 3101 has a first pixel portion 3102. The second housing 3104 has a second pixel portion 3105. The first housing 3101 and the second housing 3104 are combined with the support portion 3106 so that the e-book reader can be opened and closed by the support portion 3106. With this configuration, a paper-like operation can be achieved.

Figure 8C shows a display device 3200 for an advertisement for a vehicle such as a train. In the case of an advertising medium printing paper, the advertisement is replaced by a human hand, but by using a display device that displays the display element in a gray scale, the advertisement display can be performed in a short time without a large amount of manpower. Moreover, a stable image can be obtained without display defects.

Figure 8D shows a display device 3300 for outdoor advertising. A display device formed using a flexible substrate is popular and can enhance the advertising effect. In general, the advertisement is replaced by a human hand, but by using a display device that displays the display element in a gray scale, the advertisement display can be performed in a short time. Moreover, a stable image can be obtained without display defects.

It is to be understood that all or a part of the contents described in the embodiments may be combined with all or a part of the contents described in any of the other embodiments.

The present application is based on Japanese Patent Application No. 2009-214961, filed on Sep.

100. . . Display device

101. . . Pixel component

102. . . Source driver

103. . . Gate driver

104. . . Control department

105 ₁ to 105 _m . . . Source line

106 ₁ to 106 _n . . . Gate line

107 ₁₁ to 107 _nm . . . Pixel

111. . . Transistor

112. . . Capacitor

113. . . Electrophoresis element

121. . . electrode

122. . . electrode

123. . . Floor

124. . . White particle

125. . . Black particle

126. . . Microcapsule

600. . . Substrate

601. . . Thin film transistor

602. . . Capacitor

603. . . Electrophoresis element

604. . . Substrate

610. . . Conductive layer

611. . . Insulation

612. . . Semiconductor layer

613,614,615. . . Conductive layer

616. . . Pixel electrode

617. . . Counter electrode

618. . . Floor

620. . . Insulation

630. . . Gate line

631. . . Source line

632. . . Shared potential line

700. . . Thin film transistor

701. . . Substrate

702,707,708. . . Insulation

703a, 703b, 705. . . Conductive layer

704. . . Semiconductor layer

706a, 706b. . . Low resistance semiconductor layer

707,708. . . Insulation

3001. . . case

3002. . . Pixel section

3003. . . Operation button

3101. . . First housing

3102. . . First pixel

3104. . . Second housing

3105. . . Second pixel portion

3106. . . Support

3200, 3300. . . Display device

In the drawing:

Fig. 1A illustrates an example of a display device, and Fig. 1B shows an example of a pixel, and Fig. 1C shows an example of a grayscale storage display element.

Figure 2 shows an example of a scan signal during initialization.

Figure 3 shows an example of a scan signal during writing.

Figure 4 shows a specific example of a signal input to a pixel during switching.

Figure 5 shows a specific example of a signal input to a pixel during switching.

6A is a diagram showing an example of a top view of a pixel of a display device, and FIG. 6B is an example of a cross-sectional view of a pixel of the display device.

Figures 7A through 7D each show an example of a thin film transistor.

8A to 8D are diagrams each showing an application example of the display device.

Claims (35)

A driving method of a display device, the display device comprising a plurality of pixels each of which includes a grayscale storage display element, the driving method comprising the steps of: according to a previous grayscale level before the first initialization period, by The step of scanning and inputting the first terminal of the grayscale storage display element in the first initialization period to display the first gray scale display level, wherein the length of the holding period of each signal is weighted, and wherein the potential is shared And being input to the second terminal of the gray scale storage display element; displaying the second gray scale display by the step of scanning and inputting the first terminal to the first terminal at least once during the second initializing period after the first initializing period And displaying the first gray scale display level and the second gray scale display level by the step of scanning and inputting the first terminal to the first terminal during the writing period after the second initializing period Or a third gray scale display level between the first gray scale display level and the second gray scale display level. The driving method of the display device according to claim 1, wherein the step of performing signal scanning and inputting to the first terminals is performed once during the second initializing period. The driving method of the display device of claim 1, wherein each of the signals input to the first terminals during the first initializing period is a first potential equal to the common potential or different from the a common potential, wherein the first terminal is input during the second initializing period The at least one signal is a second potential that generates a second electric field between the second potential and the common potential, the second electric field having a direction different from a first electric field generated between the first potential and the common potential, And wherein the signal input to the first terminals during the writing period includes at least one of the common potential, the first potential or the second potential. The driving method of the display device of claim 1, wherein each of the signals input to the first terminals during the first initializing period is a first potential equal to the common potential or different from the a common potential, wherein at least one signal input to the first terminals during the second initializing period is the common potential or the second potential, which generates a second electric field between the second potential and the common potential, the first The two electric fields have opposite directions of the first electric field generated between the first potential and the common potential, and wherein the signal input to the first terminals during the writing period includes the common potential, the first potential or the At least one of the second potentials. The driving method of the display device of claim 1, wherein the common potential is input to the first terminals in the last scan of the signal at the end of the writing period. The driving method of the display device of claim 1, wherein the step of scanning and inputting the signal during the first initializing is performed x times (x is a natural number of 2 or more), and the shortest holding period of the signal is The length is t, and the length of each of the input signal hold periods is 2 ^y-1 t (y is any of x or less natural numbers). A driving method of a display device according to claim 1 of the patent scope, In the middle of the write period, the length of the hold period is the same. The driving method of the display device according to claim 1, wherein the gray scale storage display element is an electrophoretic element. A display device having a pixel portion, the display device comprising: a source driving portion; a gate driving portion; a plurality of pixels, each pixel comprising: a gray scale storage display element; and a transistor having a gate terminal electrode electrically connected to the gate a driving portion, a first terminal electrode of the transistor is electrically connected to the source driving portion, and a second terminal electrode of the transistor is electrically connected to the first terminal of the gray scale storage display element; and a capacitor having: the capacitor a first electrode terminal electrically connected to the second terminal of the transistor, and a second electrode terminal of the capacitor electrically connected to the wiring supplying the common potential, wherein according to the previous gray level level before the first initialization period And displaying, by the plurality of steps of scanning and inputting the first terminal of the gray scale storage display element in the first initializing period, the first gray scale display level, wherein the length of the holding period of each signal is weighted And wherein the common potential is input to the second terminal of the gray scale storage display element, wherein the second initialization period after the first initialization period At least one of the step of scanning and the like of the first input signal terminals, a second display level gray scale display, and wherein, the other by the second writing period after the initialization period The step of scanning and inputting the first terminal a plurality of times, displaying a third gray scale display level between the first gray scale display level and the second gray scale display level, the first gray scale display level Or the second gray scale displays the level. The display device of claim 9, wherein the step of performing signal scanning and input on the first terminals is performed once during the second initializing period. The display device of claim 9, wherein each of the signals input to the first terminals during the first initializing period is a first potential equal to the common potential or different from the common potential, The at least one signal input to the first terminals is a second potential during the second initializing period, and the second electric field is generated between the second potential and the common potential, the second electric field having a different a direction opposite to a first electric field generated between the potential and the common potential, and wherein the signal input to the first terminals during the writing period includes the common potential, the first potential, or the second potential One. The display device of claim 9, wherein each of the signals input to the first terminals during the first initializing period is a first potential equal to the common potential or different from the common potential, The at least one signal input to the first terminals during the second initializing period is the common potential or the second potential, which generates a second electric field between the second potential and the common potential, the second electric field having The first potential is opposite to the first electric field generated between the common potentials, and The signal input to the first terminals during the writing period includes at least one of the common potential, the first potential, or the second potential. The display device of claim 9, wherein the common potential is input to the first terminals in a last scan of the signal at the end of the writing period. The display device of claim 9, wherein the step of scanning and inputting the signal during the first initialization is performed x times (x is a natural number of 2 or more), and the length of the shortest holding period of the signal is t The length of each of the holding periods after the input signal is 2 ^y-1 t (y is any of x or less natural numbers). The display device of claim 9, wherein the length of the holding period after the signal is input during the writing is the same. The display device of claim 9, wherein the gray scale storage display element is an electrophoretic element. The display device of claim 9, wherein the transistor comprises an oxide semiconductor. A driving method of a display device, the display device comprising a plurality of pixels each of which includes a grayscale storage display element, the driving method comprising the steps of: according to a previous grayscale level before the first initialization period, by The first terminal scanning and input signals of the gray scale storage display elements pass through the plurality of transistors to display the first gray scale display level until each of the gray scale storage display elements is in the first initialization period When the first gray scale display level is displayed, the length of the holding period of each signal is added And wherein the common potential is input to the second terminal of the gray scale storage display element; and the step of scanning and inputting the signal to the first terminal at least once during the second initialization period after the first initialization period Displaying a second gray scale display level; and displaying the first gray scale display level, the second gray scale display level, or at the step of scanning and inputting the signal to the first terminal a third gray scale display level between the first gray scale display level and the second gray scale display level until each of the gray scale storage display elements is written during the second initialization period The third gray scale display level is displayed. The driving method of the display device of claim 18, wherein the step of performing signal scanning and inputting on the first terminals is performed once during the second initializing period. The driving method of the display device of claim 18, wherein each of the signals input to the first terminals during the first initializing period is a first potential equal to the common potential or different from the a common potential, wherein at least one signal input to the first terminals is a second potential during the second initializing period, which generates a second electric field between the second potential and the common potential, the second electric field having the a direction opposite to a first electric field generated between the first potential and the common potential, and wherein a signal input to the first terminals during the writing period includes the common potential, the first potential, or the second potential At least one. The driving method of the display device of claim 18, wherein each of the signals input to the first terminals during the first initializing period is a first potential equal to the common potential or different from the a common potential, wherein at least one signal input to the first terminals during the second initializing period is the common potential or the second potential, which generates a second electric field between the second potential and the common potential, the first The two electric fields have opposite directions of the first electric field generated between the first potential and the common potential, and wherein the signal input to the first terminals during the writing period includes the common potential, the first potential or the At least one of the second potentials. The driving method of the display device of claim 18, wherein the common potential is input to the first terminals in the last scan of the signal at the end of the writing period. The driving method of the display device of claim 18, wherein the step of scanning and inputting the signal during the first initializing is performed x times (x is a natural number of 2 or more), and the shortest holding period of the signal is The length is t, and the length of each of the input signal hold periods is 2 ^y-1 t (y is any of x or less natural numbers). The driving method of the display device of claim 18, wherein the length of the holding period after inputting the signal during the writing is the same. The driving method of the display device of claim 18, wherein the gray scale storage display element is an electrophoretic element. A driving method of a display device according to claim 18, wherein the transistor comprises an oxide semiconductor. A display device having a pixel portion, the display device comprising: a source driving portion; a gate driving portion; a plurality of pixels, each pixel comprising: a gray scale storage display element; and a transistor having a gate terminal electrode electrically connected to the gate a driving portion, a first terminal electrode of the transistor is electrically connected to the source driving portion, and a second terminal electrode of the transistor is electrically connected to the first terminal of the gray scale storage display element; and a capacitor having: the capacitor a first electrode terminal electrically connected to the second terminal of the transistor, and a second electrode terminal of the capacitor electrically connected to the wiring supplying the common potential, wherein according to the previous gray level level before the first initialization period Displaying the first gray scale display level by the step of scanning and inputting the first terminal of the gray scale storage display element through the transistor multiple times until each of the gray scale storage display elements is The first gray scale display level is displayed during the first initialization period, wherein the length of the hold period of each signal is weighted, and wherein the common potential is input to the first The second storage terminal of the display element, wherein the second gray scale display level is displayed by the step of scanning and inputting the first terminal at least once during the second initializing period after the first initializing period, and The step of displaying the first gray scale display level and the second gray scale display position by the step of scanning and inputting the signal to the first terminal a third gray scale display level, the first gray scale display level, or the second gray scale display level, until each of the gray scale storage display elements is after the second initialization period The third gray scale display level is displayed during the writing period. The display device of claim 27, wherein the step of performing signal scanning and inputting on the first terminals is performed once during the second initializing period. The display device of claim 27, wherein each of the signals input to the first terminals during the first initializing period is a first potential equal to the common potential or different from the common potential, The at least one signal input to the first terminals is a second potential during the second initializing period, which generates a second electric field between the second potential and the common potential, the second electric field having the first potential a direction opposite to the first electric field generated between the common potentials, and wherein the signal input to the first terminals during the writing period includes at least one of the common potential, the first potential, or the second potential . The display device of claim 27, wherein each of the signals input to the first terminals during the first initializing period is a first potential equal to the common potential or different from the common potential, The at least one signal input to the first terminals during the second initializing period is the common potential or the second potential, which generates a second electric field between the second potential and the common potential, the second electric field having Different from the first a direction opposite to a first electric field generated between the potential and the common potential, and wherein the signal input to the first terminals during the writing period includes at least one of the common potential, the first potential, or the second potential By. The display device of claim 27, wherein the common potential is input to the first terminals in a last scan of the signal at the end of the writing period. The display device of claim 27, wherein the step of scanning and inputting signals during the first initialization is performed x times (x is a natural number of 2 or more), and the length of the shortest holding period of the signal is t The length of each of the holding periods after the input signal is 2 ^y-1 t (y is any of x or less natural numbers). The display device of claim 27, wherein the length of the holding period after the input of the signal during the writing is the same. The display device of claim 27, wherein the gray scale storage display element is an electrophoretic element. The display device of claim 27, wherein the transistor comprises an oxide semiconductor.